Compressor unloading valve mechanism



March 11, 1941 2,234,469

COMPRESSOR UNLOADING VALVE MECHANISM Filed Nov. 8, 1939 2 Sheets-Sheet 1 FIG.|.

v IN VENTOR BURNS DICK "ATTORNEY March 11, 1941. B. DICK 2,234,469

COMPRESSOR UNLOADING VALVE MECHANISM Filed Nov. 8, 1939 2 SheetS- -Sheet 2 7/ y Wm INVENTQR URNS DICK ATTORNE;

v HR 1 v Patented Mar. 11, 1941 I PATENT OFFIQE COMPRESSOR UNLOADING VALVE MECHANIS Burns Dick, Ferguson, Mm, assignor to Wagner Electric Corporation, St. Louis, Mo., a corporation of Delaware application November 8, 1939, Serial No. 303,379

4 Claims.

My invention relates to compressors and more particularly to valve mechanism for unloading the compressor under certain conditions.

One of the objects of my invention is to pro- 5 vide an improved valve mechanism for automaticallyclosingthe intake of a compressor and connecting the discharge port to atmosphere when the pressure in the receiver of the compressor is 'a predetermined value.

Another and more specific object of my invention is to provide a mechanical connection comprising a lever between the compressor shut-off valve and thevalve for connecting the discharge port to atmosphere whereby when the'former is closed the latter will be positively and quickly opened.

Still another object is to provide a booster for association with an unloading valve mechanism of the type referred to which will assist in posi- 20 tively opening the valve for connecting the discharge port to atmosphere.

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawings in 25 which Figure l is a view, partly in section, showing a rotary compressor having associated therewith an unloading valve mechanism embodying my invention; Figure 2 is a cross-sectional view showing details of the valve mechanism; and 30 Figure 3 is a view, partly in cross section, showing a modified construction.

Referring to the drawings in detail, the rotary compressor is of known construction and com-' prises a stator I having eccentrically mounted 35 therein a rotor 2 secured to a drive shaft 3 journaled in the end plates 4 and 5. The rotor 2 is provided with a plurality of spaced slots 6 extending in an axial direction in which are mounted reciprocable blades 1 (one only'being 40 shown) biased outwardly into engagement with the inner surface of the stator by springs 8, The end plate 4 is provided with an intake passage 9 and the end plate 5 with an outlet passage l0. Secured to the end plate 5 is an oil reser- 45 voir or dome II which contains oil for the purpose of lubricating the compressor. In the construction shown the shaft 3 of the compressor drives an oil pump I! to pump oil from the body of oil through passage l3 and discharge it into 50 a well l4 through the opening IS. The oil in the wellis free to flow through the passage IS in shaft 3 and then into the compressor by way of the keyway II to thus provide lubrication for the movable parts of the compressor. In order 55 that the oil may be forced into the compressor under pressure during operation of the compressor, the body of oil in the oil dome'is caused to be subject to the fluid under pressure discharged from thecompressor. This is accomplished by having the discharge port l con nected to a. pipe l8 which extends above the oil line. An oil separator l9 removes any excess oil which may be discharged from the compressor together with the compressed air. The discharge port N has associated therewith a check valve 10 for preventing any of the compressed air from returning to the compressor.- The oil dome communicates with the compressed air receiver'or tank-2| by a conduit 22'and a check valve 23 prevents return of compressed air to the dome. The compressed air may be used for any purpose desired, as for example, the actuation of vehicle brakes.

In the type of compressor just described the compressor is generally automatically unloaded by shutting oil the intake when the receiver for the compressed air discharged by the compressor reaches a predetermined value and again allowed to compress air when the compressed air in the receiver falls to a given pressure below 25 the predetermined value. With such an arrangement, it has been discovered that when the compressor is unloaded, an excess amount of oil may be fed to the compressor and cause it to become choked" because of the compressed air acting upon the oil and forcing it into the compressor. It has also been discovered that the shutting off of the compressor by closing the intake does not cause the compressor to run idle since thecompressor still operates to compress the air remaining in the compressor which may be partially discharged into the oil dome against the compressed air already therein or, if this is not accomplished due to insufficient air to compress,

recirculated and recompressed continuously. By' 40 the compressor beingpartially under load and performing work, it will continue to generate heat and use power, notwithstanding no additional compressed air is being added to the receiver. tures present when the compressor intake is shut ofl can be eliminated to a large extent by also unloading the oil dome at the same time the intake is shut off. With the air in the oil dome under atmospheric pressure, the oil forced into the compressor will be reduced and theair and oil being circulated in the compressor will be free to be discharged into the oil domeagainst atmospheric pressure instead, of against compressed air. A superior operating compressor All of these undesirable operating fea- 45 v when no air is required to be compressed. Also the compressor will operate at a much cooler temperature, less oil will be used, and the life of the compressor extended.

My improved valve mechanism 24 comprises a casing 26 secured to the compressor adjacent the intake passage 9 by bolts 23. The casing is provided with interconnecting passages 21 and 23, the -former communicating with the intake passage 3 and the latter with atmosphere through the air cleaner 23. The passage 21 has associated therewith a valve-seat "and cooperating therewith is a valve member 3| mounted on a stem 32'which is guided in a sleeve 33 carried by a partition 34. The stem 32 projects into a chamber 35 formed by a secondary casing 33 screwed .to the main casing. Interposed between ceiver by'means of a'conduit 40. When the air pressure in, the receiver reaches a predetermined value, the valvemember 3| will be moved to closed position against the bias oi the spring 31. In the particular construction shown, the spring is of such strength that the valve member 3| will be moved toward closed position when the pressure in the receiver is one hundred pounds per square inch.

A portion of casing 25 is so formed as to provide a chamber 4| which is connected to passage 23 by a short passage 42. This connecting passage has associated therewith a valv seat 43 and cooperating therewith is a valve member 44 which is normally held seated by a spring 45. The chamber 4| is in constant communication with the oil reservoir by a conduit 43. The valve member 44' is provided with a valve stem 41 which extends across passage 23 and is guided in a bore 43 in the wall of said passage.

Within thelpassage 23 is a lever ill pivotally mounted at its center on a pin ll. One end 01' this lever cooperates with'a shoulder 52 on the valve stem 32 and the otherend of the lever is adapted to operate the valve stem 41. The concomprises a pin 53 carried by th stem and a loose washer 54 surrounding the stem and resting on the end of the lever. The position or the pin on the stem 41 is such that the lever may have limited relative movement with respect to the stem 41 before the washer abuts the pin 53 and causes movement of the valve stem. The relative movement permits the valve member 3| to move a portion of the distance toward its seat from full open position before any force can be transmitted through the lever to operate the valve stem 41.

When the compressor is operating, the parts of the valve mechanism are as shown in Figure 2. Under these conditions, air is free to pass into the compressor through the intake, be compressed and then forced out into the oil reservoir. From the oil reservoir it is free to pass through the check valve 23 into the air receiver. The oil reservoir will be sealed since the valve 44 is seated. When the pressure in thereceiver reaches a value 01 one hundred pounds per square inch, the fluid-pressure in chamber 33 :will be '44 seated. At this time the valve member 3| is compressor continues to operate and build up a the maximum pressure in the receiver at which results which will require less power to operate sufllcient to move the valve stem 32 downwardly and cause the valve member 31 to approach seat 30. When the valve stem 32 has moved downwardly a sufllcient amount to cause the relative movement between th lever 50 and the stem 3 41 to be taken up, an'added resistance will be imposed upon the movement of, the valve stem due to the action or spring 45 and the pressure in chamber 4| holding the valve member close enough to seat 30 that a slight suction will be effective on valve member 3| tending to pull it closed, this suction being created by the continued operation'oI-the compressor. As the small additional amount or pressure in the receiver and also in chamber 36, the stem 32 will be moved downwardly an additional extent. This additional movement of the stem will now cause the-lever to move the valve member 44 of! its seat and release 'the pressure in chamber 4|. When this occurs, the resistance to movement 01 the valve stem 32 is considerably decreased and the'valve member 3| will move very rapidly onto its seat, which movement will be assisted by the vacuum pull on the valve member as it 1 approaches the seat.

compressed air in the oil receiver is thus vented.

With the intake shut off, no more air will enter the compressor and any air that is already in the compressor will be readily forced out through the check valve 23 at the'discharge port since there is now no compressed air pressure acting on this valve to hold it seated in addition to its spring. Since the compressor is no longer compressing any air, it will run idleand the power necessary to rotate it will be decreased to a minimum. Also, due to the fact that the blades are no longer performing any compressing, the temperature of the .compressor will drop rapidly'as will also the oil in the compressor and the reservoir. Since the interior of the oil reservoir is at atmospheric pressure, the oil in well- |4 will no longer be positively forced into the comprese sor. The amount or oil entering the compressor by the force of gravity and the effect of suction in portions of the compressor will now be a minimum and there will be little danger of the compressor becoming choked with oil during its unloading period.

When suillcient air is used from the compressed air receiver 2| to cause the pressure therein and also in chamber 35 to drop to such a low value that spring 31 can move valve member 3| oil. its seat against the forces acting to hold it closed. The intake will again be opened and the oil reservoir sealed by the closing of the valve member 44. The compressor can now operate to restore.

time the compressor will again be shut off and the oil receiver vented to atmosphere in a mannerv already described.

In Figure 3 there is disclosed a modified con- 1 struction wherein a booster is associated with the oil reservoir venting valve in order to" assist in opening it at the proper time against the fluid pressure in the oil reservoir tending to maintain it closed. In the construction shown, the intake shut-on valve is the same as already described.

58 is also connected to the end of the valve stem l and this bellows isplaced in constant communication with the conduit 40' by a branch conduit 59. The bellows is thus subject to the same fluid pressure as that inthe air receiver. The

of the intake valve member 3| (Figure 2) is operatively connected to the valve member 41' through a spring 80, such spring being inter: posed between two washers 6|, one of which engages a pin 53' by the valve stem'and the other of'which rests on the end of lever 50'.

value of one hundred pounds per square inch and causes the intake valve member}! to move toward closed position, the lever 50' will com-' 25 press the spring 60 and apply a ,forc'etending to open the valve member 44'. At the same time the pressure eflective in the Sylphon bellows 58 will also so act as to tend to move the valve member 44' oil its seat against the bias of the spring 5'! and the fluid pressure in chamber ll. When the valve member Si is just reaching its seat to close on the'intake, the pressure applied by the lever 58' and the fluid pressure eflective in the Sylphcm bellows will snap the valve member 44' oil its seat, thereby venting the oil reservoir to atmosphere. By the use of the for opening the valve 44', the force necessary to be applied by the lever to open the valve is decreased, thus resulting in removing a portion (0 oi. the load off the fluid motor acting to close the valve 3| and permitting this valve to have a smoother operation.

Being aware of the possibility of other modiflcations in the particular structures herein de- 65 scribed, without departing from the fundamental principles oi my invention, 1- do not intend that their scope be limited except as set forth by the appended claims.

Having fully described my invention, what I 50 claim as new and desire to secure by Letters Patent of the Unitedstates is:

1. In compressed air storage apparatus comprising a receiver and an air compressor provided with intake and discharge ports, automatically operable means for closing the intake port and connecting the discharge port to atmosphere; said means comprising a valve casing provided with a e for placing the intake port'in communication with the atmosphere, a normally so open valve associated withv said passage, a fluid Q motor for closing said valve when the fluid pressure in the receiver is a predetermined value;

meansincludingsaidpsssageior the discharge port to atmosphere, a normally closed lever 50' which is operated'by the valve stem 32.

When the pressure in the receiver reaches a valve, and means-comprising a lever positioned in said passage and operatively connected to the valves for causing the opening of the second valve when the first valveis closed.

2. In compressed air storage apparatus comprising a receiverand an air compressor provided with intake and discharge ports, automatically operable means for closing the intake port and connecting the discharge port to atmosphere, said means comprising a spring biased normally open valve for closing the intake, a fluid motor for closing said valve when the fluid pressure in the receiver is a predetermined value, a normally closed valve for placing the discharge port in communication with the atmosphere and movable to open position against fluid pressure, and means for causing the closing movement of the first named valve to open the, second named valve and comprising a lever interconnecting the movable'elements of the valves and embodying a lost motion connection permitting partial closing oi the first named valve prior to any movement of the movable element of the second-named valve to open position.

3. In compressed air storage apparatus comprising a receiver and an air compressor provided with intake and discharge ports, automatically operable means for closing the intake port and connecting the discharge port to atmosphere,

said means comprising a valve for. closing the intake, a second valve for placing the' di'scharge port in communication with theatmosphere and movable to open position against compressed air,

means controlled by a predetermined pressure in the receiver for closing the flrst valve, means controlled by fluid pressure tending to open the second named valve, and connecting means operable by the closing means of the-first named valve for causing opening the second named valve with the assistance of the last named fluid pressure controlled means. 4. In compressed air storage apparatus com-J prising a receiver and an air compressor provided with intake .and discharge ports, automaticallyoperable means for closing the intake port and connecting the discharge port to the source of fluid to be compressed, said means comprising a normally open valve for closing the intake, a

fluid motor for closing said valve when the fluid pressure in the receiver is a predetermined value, a normally closed valve for placing the discharge port in commimication with the source oi fluid,

means i'or causing the, closing movement of the first named valve to apply an opening forceto.

the second named valve and comprising a lever interconnecting the -movable elements of thev valves and embodying a yieidable connection per,-

mitting partial closing of the first named valveprior to movement of the movable element of the second named valve to open position, and a fluid pressure-operated booster for assisting the opening of the second named valve.

' .aurms'nr cx. 

